The development of spermatogonia includes a characteristic sequence of events culminating with the formation of a highly complex differentiated cell - a spermatozoon. The molecular processes involved in the germ cell determination and differentiation are not well understood. With the aid of a newly developed electrophoretic technique, we have detected new basic proteins in the spermatogenic cells of the mouse testis. The presence of testis-specific histone H1b can be correlated with the early determination of germ cells; whereas, H2S and protein "A" appear to be involved in some specialized event unique to the primary spermatocyte during spermatogenesis in the mouse. The proposed studies will involve isolation and purification of testis-specific basic proteins and their variants. The purified protein fractions will be biochemically characterized and used to generate specific antisera in the rabbits. The specific antisera will be utilized for the localization and quantitative estimation of the individual proteins. The specific antisera will be used to isolate histone specific mRNA's from the spermatogenic cells. The specific mRNA's will be utilized for the synthesis of cDNA probes which would in turn be used to probe the regulatory aspects of the testis-specific proteins. In addition, the biosynthetic aspects of the testis-specific basic proteins will be investigated by in vivo labelling and radioimmunoassay.